Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-05-10
2004-02-17
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S502000, C313S506000, C313S509000, C257S088000, C257S093000, C257S100000
Reexamination Certificate
active
06692845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to light-emitting devices. More particularly, the present invention pertains to a light-emitting device comprising an element (hereinafter referred to as “EL element”) in which a thin film of a light-emitting organic material (hereinafter referred to as “organic EL film”) that can attain electro luminescence (hereinafter also referred to as “EL”) is interposed between an anode and a cathode. Examples of such light-emitting devices according to the present invention include an organic EL display and an organic light-emitting diode (also referred to as “OLED” in short).
Light-emitting materials which can be used in the present invention encompass all light-emitting materials that can emit light (phosphorescence and/or fluorescence) via at least one of a singlet excitement and a triplet excitement.
2. Description of the Related Art
Since Eastman Kodak Co. announced that a light-emitting device using an organic EL film had emitted light at a low drive voltage, the light-emitting device using the organic EL film has been noticed. According to an announcement by Eastman Kodak Co., it is characteristic to decrease the drive voltage by taking a laminate element structure; therefore, many companies have conducted research and development on such laminate element structure.
Though the organic EL film is individually used as a luminescent layer in some cases, it, ordinarily, forms an EL element in combination with an organic material such as a hole injection layer, a hole transport layer, an electron transport layer or an electron injection layer. On this occasion, the organic EL film includes a polymer-typed organic EL film and a low molecular weight-typed (monomer-typed) organic EL film.
Generally, in the present specification, polymer-typed organic materials are referred to as polymer films whereas low molecular weight-typed organic materials as low molecular weight films so that polymer-typed organic EL films are the polymer films whereas low molecular weight-typed organic EL films are the low molecular weight films.
Now, a structure of the EL element, on which the present inventors has run a test, is shown in FIG.
2
. In
FIG. 2
, an anode
202
comprising an indium tin oxide (ITO) film is provided on a substrate
201
; on the thus provided anode
202
, provided are a hole injection layer
203
comprising polythiophene (PEDOT), a luminiscent layer
204
comprising poly(p-phenylenevinylene) (PPV) and a cathode
205
comprising a metallic film in sequence in a direction of departing from the anode
202
.
As a result of a careful observation by the present inventors on the EL element of a trial production with the structure shown in
FIG. 2
, many pinholes and delaminations were found in the cathode
205
. Further, it was found that such pinholes and the like had caused a dark spot (deteriorated portion in black dot form) of the EL element. That is, the dark spot derived from a defect of film formation of the cathode
205
has remarkably deteriorated a displayed image quality.
The present inventors have considered that such pinholes or delaminations of the cathode
205
are caused by a poor adhesion between the luminiscent layer
204
comprising the polymer film and the cathode
205
comprising the metallic film. That is, the present inventors have considered that, since the polymer film such as PPV is hydrophobic, it shows a poor adhesion with the metallic film thereby causing a pinhole or delamination at the time of the film formation of the cathode
205
.
SUMMARY OF THE INVENTION
Under such circumstances, it is an object of the present invention to provide a technique for forming a film of a cathode comprising a metallic film with a good adhesion in an EL element with a polymer film as a light-emitting layer or an electron transport layer. It is another object of the present invention to provide a light-emitting device with a favorable displayed image quality to be produced by utilizing the technique.
The present inventors have considered that the adhesion can be improved by not performing a film formation of the metallic film directly on a polymer film but by providing a low molecular weight film on the polymer film as a buffer for the purpose of improving the adhesion and then providing the metallic film on the thus provided low molecular weight film.
That is, when a luminescent layer is the polymer film, the low molecular weight film is provided as an electron transport layer or an electron injection layer and then the cathode comprising the metallic film may be provided on the thus provided low molecular weight film. Further, when the electron transport layer is the polymer layer, the low molecular weight layer is provided as the electron injection layer and then the cathode comprising the metallic film may be provided on the thus provided low molecular weight film.
REFERENCES:
patent: 6150668 (2000-11-01), Bao et al.
patent: 6194119 (2001-02-01), Wolk et al.
patent: 6320322 (2001-11-01), Tanaka
patent: 6537687 (2003-03-01), Nii
patent: 6551723 (2003-04-01), Okada et al.
patent: 2002/0113248 (2002-08-01), Yamagata et al.
patent: 2002/0185967 (2002-12-01), Friend
patent: 0 993 235 (2000-04-01), None
patent: 11-271753 (1999-10-01), None
Kido J. et al., “Bright blue electroluminescence from poly (N-vinylcarbazole)”, App. Phys. Lett. 63 (19), Nov. 8, 1993, pp. 2627-2629.
S. Miyashita et al.; “Full Color Displays Fabricated by Ink-Jet Printing”;Asia Display/ IDW '01; pp. 1399-1402; 2001.
Ikeda Hisao
Maruyama Junya
Fish & Richardson P.C.
Garrett Dawn
Kelly Cynthia H.
Semiconductor Energy Laboratory Co,. Ltd.
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